[Eeglablist] Oddly "Wavy" Data

[Matthew Stief]

Thanks again Andrew.

As for the 1hz filter, my study is a lean mean P1 isolating machine.  I am
relying on this paper that found that N70-P100 amplitude was only very
slightly attenuated by a 1hz filter and only became very seriously
attenuated as it approached 8hz.

Skuse, N. F. & Burke, D. (1990).  Power spectrum and optimal filtering for
visual evoked potentials to pattern reversal.  *Electroencephalography and
Clinical Neurophysiology, 77, 3*, 199-204.

http://www.sciencedirect.com/science/article/pii/016855979090038F

-M





On Mon, Feb 27, 2012 at 3:33 PM, ANDREW HILL <andrewhill at ucla.edu> wrote:
>
> Just looks like Alpha to me.. e.g. normal and not a problem.
>
> Of course, filtering at 1hz will cause other problems with your ERPs.
>
> Best,
>
> andrew
>
>
>
>
> Going back to the same dataset before any processing has been done, you
can see the same waves.  Obviously this is not particularly clean data, but
is it salvageable?
>
>
http://s1153.photobucket.com/albums/p512/mstief/?action=view&current=wavychannels8.jpg
>
>
> Here's the exact same stretch of data after it has gone through 1hz high
pass and 55hz low pass filters.
>
>
http://s1153.photobucket.com/albums/p512/mstief/?action=view&current=wavychannels10.jpg
>
>
> It does seem to be affecting the ERPs at least to my untutored eye,
here's one channel.
>
>
http://s1153.photobucket.com/albums/p512/mstief/?action=view&current=wavychannels4.jpg
>
>
> So what is it?  Normal?  Horrible?  Fatal or merely deleterious?  Given
that it seems to contaminate most or all of the data for this person should
I just throw it out or can I get something out of it?  In particular how
will ICA handle it?  Do I still have a chance of getting a stable
decomposition out of it with a reliably identifiable P1?  This person was
particularly bad but there are less drastic examples in several of my other
participants.  Keep in mind some of my participants are rather rare and
would be difficult to replace (I study sexual orientation and some
varieties are less common than others).
>
> --
> _________________________________________________________________
> Matthew Stief
> Human Development | Sex & Gender Lab | Cornell University
> http://www.human.cornell.edu/HD/sexgender
>
>
> Heterosexuality isn't normal, it's just common.
> -Dorothy Parker




--
_________________________________________________________________
Matthew Stief
Human Development | Sex & Gender Lab | Cornell University
http://www.human.cornell.edu/HD/sexgender


Heterosexuality isn't normal, it's just common.
-Dorothy Parker
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